SAN DIEGO -- The Indianapolis Colts' defensive unit has been in a good mood inside the locker room after most games this season.

That wasn't the case at Qualcomm Stadium on Monday night.

There was lots of talking among each other with voices lowered more than 45 minutes after the Colts' 19-9 loss to the San Diego Chargers.

The Colts had pushed the “bend, but don’t break” mind frame most of this season. That style finally caught up to them against the Chargers, and they can only blame themselves.

Penalties to give the Chargers first downs. Quarterback Philip Rivers making the necessary throw to keep a drive going. Running back Ryan Mathews finding a crease in the defense to run for 15 yards.

“We were shooting ourselves in the foot,” Colts defensive tackle Ricky Jean Francois said. “We were getting the looks we wanted in every area, but we weren’t executing. It was a good example of not executing against a good quarterback. You were only going to get a look one time, and once that one opportunity was gone, they were going with it.”

Controlling the line of scrimmage and getting off the field on third down to give quarterback Andrew Luck plenty of time on the field is what the Colts have talked about on a regular basis.

They failed to accomplish their goal.

The Chargers were 7-of-14 on third down and ran for 147 yards, including 102 from Mathews.

Stopping the run didn’t suddenly become a problem on Monday.

The Colts have allowed 246 yards rushing between the tackles in their past two games. That total is only a yard less than they allowed in the first four games of the season.

“The first thing we always say is control the line of scrimmage,” Colts safety Antoine Bethea said. “They were able to run, but as a unit we have to play better. That’s what it is. We set our standard high and we didn’t play up to that.”

Not making the necessary stops allowed San Diego to control the clock. The Chargers had possession for 38 minutes and 31 seconds, keeping Luck watching on the sideline. The Colts gave up first downs on plays of at least 10 yards on third down twice and were called for penalties on third down twice.

“We couldn’t get off the field,” Colts coach Chuck Pagano said. “We held them to a touchdown and then forced the field goals, but time of possession, that just killed us.”

You knew the Colts were in for a long night when Rivers was being lauded.

Until Monday night, Ryan Mathews had not rushed for more than 100 yards since October 2011. AP Photo/Denis Poroy

Rivers is a pocket-passer. That meant Robert Mathis should have been able to add several sacks to his total, right?

Wrong.

Mathis knew that. That’s why he spent most of last week talking about how dangerous Rivers is. The Chargers quarterback is now 4-0 against the Colts in the regular season.

Rivers kept the Colts off balance by constantly changing up his snap count, and he made quick throws against the sixth-best pass defense in the league.

Rivers was 22-of-33 for 237 yards and was sacked only twice. He didn’t even have to force the ball to tight end Antonio Gates. Receiver Keenan Allen was Rivers’ go-to target. He had nine catches for 107 yards.

“Philip Rivers strikes again,” Mathis said. “I’ve been around him long enough and I know that’s what he’s capable of. We weren’t able to get to him enough, and he converted those critical third downs. He has that clock that all good quarterbacks have. He was able to get it out there.”

Don’t worry, the Colts only have to face quarterback Peyton Manning on Sunday. Yes, the former Colt who is on pace to rewrite the record books this season.

“You have to make plays,” Jean Francois said. “If you don’t do it against quarterbacks like Rivers, and next week you know who we’re playing, they can jump on you. We were frustrated because we know we were doing it ourselves. They’re a good team, hats off to them.”